Neutron detectors are used in a variety of applications, such as physics research, geophysical applications, security screening, military applications, or the like. Typical neutron detectors make use of scintillators, which are materials that emit light upon interaction with radiation particles. The light passes to a photodetector device, such as a photomultiplier tube, which converts the photons (light) emitted from the scintillator into electrical pulses. The electrical pulses can be processed by associated electronics and may be registered as counts that are transmitted to analyzing equipment.
Helium-3 neutron detectors are the accepted standard in neutron detectors. Unfortunately, however, the availability of 3He is very limited when compared to the worldwide demand.
Organic scintillators in the form of solid, machinable plastic materials are widely available and have a number of significant advantages in terms of cost, performance, and the ease at which plastic scintillators can be shaped, through the use of molds or other means, into virtually any desired shape or size. Unfortunately, however, detectors using plastic scintillators tend to have a much greater response to gamma rays than 3He neutron detectors. A higher sensitivity to gamma rays can result in too many false positive counts where a gamma ray interaction is incorrectly identified as a neutron interaction. Because the presence of neutrons typically indicates the presence of fissile materials while gamma rays can be emitted from non-fissile, but naturally radioactive materials, the ability to accurately distinguish between the two types of particles is critical for security and nuclear safety applications.
A variety of pulse-shape-discrimination (PSD) techniques have been developed to distinguish between neutron and gamma events for certain types of detectors. But while these techniques work well for liquid organic scintillators, PSD has been difficult or even impossible to use for solid organic (plastic) scintillators.
Accordingly, further improvement of neutron detectors, particularly neutron detectors using solid organic scintillators, is desired.